Methods: In nine anaesthetised ferrets the left lingual nerve was sectioned and recovery permitted for 3 days, 3 weeks or 3 months (3 ferrets/group). Three days before the end of this period, the retrograde tracer Fluorogold was applied to the inferior alveolar nerve to label its cell bodies in the trigeminal ganglion. After the recovery period, under anaesthesia (sodium pentobarbitone 42mg/kg i.p., maintenance 3mg/kg i.v.), the animals were perfused with fixatives. Fourteen micron-thick cryostat sections were processed using indirect immunofluorescence, and the proportion of Fluorogold-positive cells that were labelled for TRPV1 was quantified.
Results: In controls the mean proportion of inferior alveolar neurones (± 1SD) that were TRPV1-positive was 10.9 ± 1.1%. Three days after lingual nerve section this proportion had significantly increased to 15.5 ± 0.9% (P = 0.005, ANOVA); the figures for 3 weeks and 3 months survival were 14.0 ± 2.7% (P > 0.1) and 15.9 ± 1.6% (P < 0.02), respectively.
Conclusion: Lingual nerve section caused a significant increase in the proportion of inferior alveolar neurones that were labelled for TRPV1. These data suggest that changes in TRPV1 expression in uninjured afferents may be involved in the sensory disorders that follow trigeminal nerve injury.